1. Field of the Invention
The invention relates to energy-absorbing bumpers mounted on legs or other structural members of oil rig platforms, barge loading docks or similar structures to fend off vessels from or to rig structures or barges or other floating vessels which may be berthed at the rig structures from damage which can result from relative motion between a floating vessel and a rig structure as a result of wave action.
More particularly the invention relates to a new rubber bumper cushion sleeve construction rotatably mounted in a stacked series of sleeves on a typical usually vertical bumper pipe member which is supported outboard in any usual manner on a platform leg or other similar structural member.
Further, the invention relates to a series of rubber sleeve members stacked in an interfitting manner and rotatably mounted on a vertical metal bumper pipe member and to the particular dimensional and constituent materials construction and content of such sleeve members to provide an outer abrasion or tear resistant contact surface, an inner hard, load supporting layer, which may have a relatively low friction surface and an internal annular soft energy-absorbing body portion.
2. Description of the Prior Art
There have been a great variety of types of prior barge bumpers wherein the vertical metal pipe member has a stack of used automobile or other vehicle tires rotatably mounted on the pipe member between top and bottom pipe member supports. Such stacked tire bumpers are characterized by deficiencies in that the bumper may be engaged by a boat rib which forces its way in between two adjacent tires, and during wave action such engagement may rip one or more of the tires off of the bumper pipe member requiring repairs for the bumper and replacement of tires.
These deficiencies in stacked tire bumpers have been sought to be overcome by replacing the tires using specially molded tire-substitute doughnutlike disks or rings having 9" to 12" axial thickness and having special configurations to permit rotative mounting on the bumper pipe member, such rings having flat ends and outer diameters considerably larger than the axial ring thickness. Examples of such specially mounted energy-absorbing bumper rings are shown in U.S. Pat. Nos. 3,145,685, 3,873,076, 3,991,582, 4,005,672, 4,098,211 and 4,109,474.
Problems that have been encountered in the use of such special energy-absorbing flat ended large diameter tire replacement rings have led to the use of a continuous molded rubber pipe having an internal diameter larger than the outer diameter of the metal bumper pipe and having a length approximating that of the metal bumper pipe telescoped over, surrounding and rotatably mounted on the metal bumper pipe. Such protective rubber pipes may, for example, be 20 feet long.
Such energy-absorbing rubber pipe members avoid the difficulties encountered with other forms of rubber tires or rubber rings stacked on the metal pipe member described; but when such long rubber pipe members may fail or be torn or otherwise damaged by rubbing abrasion from the ribs of a barge or other floating vessel, extremely high cost replacement procedures are involved.
That is to say, the bumper must be dismantled at least at its upper end from its support on the rig structure so that the damaged rubber pipe can be telescopically removed from the upper end of the bumper metal pipe and a new rubber pipe telescoped onto the metal pipe from the top. Such replacement requires the use of heavy handling equipment to accommodate the weight and long length of the rubber pipes being removed and replaced.
Accordingly, there is an existing need and a long standing want in the field of barge bumpers for offshore oil rigs for a rubber bumper construction which may be rotatably mounted on a vertical oil rig metal pipe member which avoids the difficulties heretofore encountered with prior devices and which functions in an efficient and reliable manner to resist abrasion, to rotate easily on the bumper pipe, and to cushion forces to which the bumper is subjected by barges, boats and their ribs when berthed at an offshore rig structure and moving relatively with respect to the rig structure, for example, due to wave action.